minimum density

[baran khaksari]

Hi,

My simulation continued till 135.99sec then FDS showed "Warning minimum density, 0.120 kg/m3, clipped in Mesh 1" and the simulation stopped because of numerical instability. 

Is the numerical instability because of the warning? If yes, how can I solve it?

Many thanks,

Baran

[fde]

Numerical instability is the outcome of the warning. The warning is just informing the density is too low (e.g. excessive depressurization). Have you checked  4.2 Common Error Statements?

[Baran Khaksari]

I checked 4.2 but none of the items in the "Numerical Instability Errors" section is not about the low density.

--
You received this message because you are subscribed to the Google Groups "FDS and Smokeview Discussions" group.
To unsubscribe from this group and stop receiving emails from it, send an email to fds-smv+u...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/fds-smv/48c91654-35b0-4535-91ae-eede33b13f73n%40googlegroups.com.

[dr_jfloyd]

You need to consider what impact the values you give for inputs will have in the simulation.

What determines the density of a gas?  It is the number of moles of gas per volume.  If volume is fixed, you can get a low density by removing gas. If the volume is not fixed (i.e., an OPEN boundary is present), then you can get low density with high temperature.

CONVECTIVE_HEAT_FLUX=612.50

To get a convective heat flux of of 612 kW/m2 with typical heat transfer coefficients of 10 to 100 W/m2/K what delta T between the surface and the gas is required?   6120 to 61200 K. The highest known melting point of any material is ~4000 K.